The present invention relates to a magnetic bubble memory device and, more specifically, to a transfer gate of a major-minor loop-organized magnetic bubble memory device.
Recently, there have been a number of proposals for approaching to a 4 .mu.m or less high density magnetic bubble memory device. The most efficient one of the proposed approaches is a bubble device comprising: a magnetic layer having a first region having the easy axis of magnetization extending in a certain direction and a second region surrounding said first region and having the easy axis of magnetization substantially perpendicular to that of the first region, said first region defining at least one major loop pattern for propagation of information bubbles and a plurality of minor loop patterns for storage of information bubbles; and an electrical conductor pattern deposited on said magnetic layer with an insulating layer interposed therebetween in a region in which the major loop pattern and the minor loop patterns are opposed to each other, thereby constructing a transfer gate for transfer of information bubbles between the major loop pattern and the minor loop patterns. The second region of the magnetic layer is, in general, made by ion-implantation to the magnetic layer. The major loop pattern and the minor loop patterns are contiguous patterns which may be composed of a plurality of overlapping disk or square patterns.
In a conventional device of the above-mentioned type, however, there is a problem that the operating characteristics of the transfer gate, that is, the bias field margins, the phase margins and the transfer current margins are insufficient for various reasons which will be discussed in detail subsequently, with reference to the drawings. This problem makes it difficult to realize a 4 .mu.m period device.